Angiogenin is a human protein which induces blood vessel formation (Fett et al. 24 Biochemistry 5480, 1985). This biological activity is expressed with an amount as low as 35 fmol (using a chick embrYo CAM assay procedure, Id.). Although originally isolated from medium conditioned by human tumor cells,aangiogenin is not tumor specific, can be found in a variety of other cells and biological fluids, and most likely plays a role in normal and/or pathological neovascularization. It has a molecular weight of about 14,400 and an isoelectric point greater than about pH9.5, Id. Strydom et al. 24 Biochemistry 5486, 1985 also disclose the amino acid sequence of angiogenin.
Angiogenin is known to have an enzymatic activity. Specifically, it catalyzes limited cleavage of 28S and 18S rRNA to produce a specific pattern of products of 100-500 nucleotides in length (Shapiro et al., 25 Biochemistry 3727, 1986), but it has no significant ribonuclease activity in standard RNase assays, Id.